Sizing at Output or Calculation Time

You may control when the tray calculations are performed and whether the column pressure profile is updated by selecting the desired calculation option.

Normally, tray sizing is calculated after the flowsheet calculations are complete, at output time. This is the default calculation method. Select the During Column Convergence and do not update pressure profile option to request that tray calculations are completed for each convergence cycle through the column. This option makes the tray sizing results available to other unit operations.

Select the During Column Convergence and update the pressure profile option to request tray calculations during each convergence cycle through the column with the calculated tray pressure drops used to update the column pressure profile for the calculations. The column pressure profile is converged as well as the column equations. A scale factor may be supplied to convert the calculated tray pressure drops from a theoretical tray basis to an actual tray basis. For example, if an overall tray efficiency of 80 percent is used to determine the number of theoretical trays in the model, a scaling factor of 0.80 is supplied to increase the calculated pressure drops to correspond to the actual number of trays in the column. You can enter the desired scale factor in the highlighted field, replacing the default value of 1.0.

Note: From v10.1, During Column Convergence and Update the Pressure Profile option is the default option in GUI for new Sizing section.